Pulse-burst Particle Image Velocimetry (PIV) has been employed to acquire
time-resolved data at 25 kHz of a supersonic jet exhausting into a subsonic
compressible crossflow. Data were acquired along the windward boundary of
the jet shear layer and used to identify turbulent eddies as they convect
downstream in the far-field of the interaction. Eddies were found to have a
tendency to occur in closely-spaced counter-rotating pairs and are routinely
observed in the PIV movies, but the variable orientation of these pairs
makes them difficult to detect statistically. Correlated counter-rotating
vortices are more strongly observed to pass by at a larger spacing, both
leading and trailing the reference eddy. This indicates the paired nature of
the turbulent eddies and the tendency for these pairs to convect through the
field of view at repeatable spacings. Velocity spectra reveal a peak at a
frequency consistent with this larger spacing between shear-layer vortices
rotating with identical sign. Super-sampled velocity spectra to 150 kHz
reveal a power-law dependency of -5/3 in the inertial subrange as well as a
-1 dependency at lower frequencies attributed to the scales of the dominant
shear-layer eddies

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2015.DFD.L21.2